Aircraft power systems generate, regulate and distribute power throughout an aircraft. Aircraft power differs from ground based utility systems in a number of ways; two of the most obvious are DC and AC power. In an aircraft the DC power is based on 28 V DC rather than the 12 VDC power in an auto, or other ground based vehicles. For AC power the frequency of operation is 400 Hz as opposed to 60 Hz in ground based utility systems. An important difference is also in reliability. If power goes out in your home the consequences are rarely catastrophic. If power goes out in an aircraft in flight the consequences can be disastrous. This is especially trues since the electronics content in aircraft has been increasing, and even the control surfaces may be actuated by electronics in so called fly by wire systems.
The need for reliability tends to call for power systems that are immune to generator failure and other failures that would cause a loss of aircraft power.
Aircraft power systems can include auxiliary power units that provide power when main engines are not running and complete electrical power generation and conversion systems that provide essential power for aircraft operation. Unlike a ground based public utility user the aircraft system is self-contained as the generating system, distribution system as well as the loads are present on the airframe.
In normal aircraft operation, the propulsion engines drive the generators to produce electric power. In case of total engine failure the aircraft would have a total loss of engine power and generator output. The use of emergency power systems can enable critical aircraft systems to continue operating until the aircraft is safely landed. Accordingly safe and reliable power distribution systems for aircraft may be desirable.